D-Jetronic Problem!!!!!

Hi. I have asked BOSH to solve it for me, but no reply from them yet. The reason I do not want to ship the MAP to them again is because I would need to contact a local garage and go through a troublesome shipping process, as BOSH does not work with retail customer. Therefore, I would like to seek alternative solution here if possible.

Attached the estimate from BOSH: drive.google.com/file/d/1ZeeZHL8Yr9wLr8J...Jqr/view?usp=sharing
Attached my follow-up email to BOSH regarding the issue: drive.google.com/file/d/1m7U42NSVswN8K3A...2sy/view?usp=sharing

Thanks!

Hi,

that is very interesting that they tested your ECU and MAP sensor, found nothing and replaced "age related" components at a special price. Normally they charge more than 900€ for repair.

However they have tested your MAP sensor as they write. So you should trust it and you cannot test it any better than them. You can verify windings resistance and vacuum leakage. To me it looks like you have another problem with your engine mechanics, ignition, wiring or D-Jetronic. Your ECU and MAP sensor seem okay even before you sent them to Bosch. They dound no problem with both.

Thanks for your advice! Before sending to BOSH for repairing, I have checked according to your recommended list (e.g., compression, valve clearance, valve timing, ignition distribution firing timing, ignition wire/ cap, ECU wiring, other related sensor). After they returned, it is perfect. There is only one problem regarding idling mixture being lean. To my limited knowledge, any error in the above list should not only apply to idling exclusively.

Maybe I am missing something here. Appreciate any comment/ input. For now, let me run another check according to the list and get back to you if any update. Thanks!

P.S. I think it worth the price. And, btw am I picking bones out of egg here?

Hi there! Hope you guys are doing well. Good to be back to this informative forum and keep up my learning. I have taken advice from Dr-DJet, checking compression, compression leaking, vacuum, valve timing, timing chain, valve clearance, ignition system, ignition timing, and they are in good condition. Please advise if anything I missed here for the check-up.

After spending few months reading through and check according to the articles and comments here, here are some observations and questions that I would like to seek help from experts here:

1) I have check the ohm and continuity of all pins at the ECU connect plug. All pins are on par with the specification suggested by the Dr-DJet's checklist. Only Pin 18's start signal has only 9.9v, which is below 11.5v suggested by the forum. Does any expert here know if this situation will cause the leanness problem of my car?

2) I tried to disconnect air temperature sensor, the CO will go up to 6.6%. Then, I turn the CO leaner at the ECU, which bring the CO to 3%. However, when the the car hits 2000~2500 RPM, the CO was 4.5%, which I think is too rich in this case. May I know what would be the adverse effects if I keep the car without air temperature sensor (running rich instead)?

3) Can I turn fuel pressure 2.1 bar, would it drives up the CO while idling? Any adverse effects if I drive up the CO in this way?

Any comments and suggestions are well appreciated! Thanks again for your help in advance!

Hi,

in which range can you adjust CO if you leave air temp sensor on connector?

Thanks for your prompt reply! Below are the data of the CO with air temp senor plugged in to the connector.

Under engine's operating temperature 80~85 degree celsius & there are total 20 clicks at the knob of ECU from the left (the leanest) to the right (the richest):

The 20th click (the richest and to the far right): CO 0.8~0.9% during idling
The 10th click: CO 0.16~0.20% during idling (the engine starts to die during deceleration at this and below clicks)
The 1th click ( the leanest and to the far left): CO 0.15%

The ignition timing 0 degree to 5 degree BTDC
The MAP vacuum leakage is perfect (~0.5-0.49 bar for more than 10 sec.)
The idling RPM is 720~800 with a little bit hesitation, and the exhaust is not continuous with intermittent popping sounds

Hope these reference points are helpful!

Hi,

can you tell me hiw your CO is when you disconnect throttle switch?

All this sounds strange as if tuning of MAP sensor was wrong. If it was not repaired by Bosch itself I would claim that it was done wrongly.

Thanks for your instruction! Below are the performance data of the car:
When engine operating temperature reached 82~85 degree celsius & disconnect wires connector on throttle switch, then start and running engine at RPM 850~900 with CO 2.7% (0.55 bar vacuum during idling)

After 2 mins of running, RPM 730~820 with CO 0.19~0.20%
After 5 mins of running, RPM 730~820 with CO 0.17~0.18%
After 10 mins of running, RPM 730~820 with CO 0.17~0.18%
After 15 mins of running, RPM 730~820 with CO 0.17~0.18%
There is no change since then, so I turned off engine

Regarding the suspicion of the faulty MAP sensor, I hope it is not the case, cause it is not about the price, but it is too troublesome to communicate with BOSH service center for rechecking and retuning, as they have not replied me yet.
May I humbly ask if you would recommend me to return the MAP senor to BOSH for rechecking and retuning or buy a new/rebuilt MAP sensor? Thanks~

Hi Danny,

as you tested all sensors okay and a vacuum leak would rather create higher than lower CO I am a bit puzzled. Normally I would now be supsicious about MAP sensor and maybe ECU. But as it was tested okay by Bosch, I have to think of other possibilities why your car would run so lean.

Fuel pressure and injectors are okay?

Thanks for your prompt reply! Below are the data regarding fuel pressure and injector:
Fuel pump's parts number: 0580464042
Fuel pump connector with 12.6 V when engine idling
I use battery to power 12V to fuel pump (it released 1.5L fuel in 30 sec.)
Fuel system pressure 1.9~1.95 bar when engine idling
after ignition off 5 mins: 1.7bar system fuel pressure
after 10 mins :1.5bar system fuel pressure
after 15 mins: 1.2bar system fuel pressure
After 20 mins: 1.0bar system fuel pressure
After 25 mins: 0.8bar system fuel pressure
After 30 mins: 0.5 bar system fuel pressure

I just received the ALLSUN EM276 injector tester that I purchased earlier, and I am planning to take out all injectors to check the spraying pattern of each injector. However, there are 4 modes for me to choose for checking injector:
1) output 1 pulse, whose pulse width is about 250ms
2) output 50 pulses, every pulse's pulse width is about 7ms
3) output 100 pulses, every pulse's pulse width is about 3.5ms
4) output pulses continuously at the rate of 50 pulses per about 1450ms, every pulse's pulse width is about 7ms

May I know which mode would be the most accurate and secure for the injector checking? Anything I should be aware of? Thanks again~

Hi Danny,

I cannot comment on Sun injector tester. Remember it must not apply 12V pulses !

Your holding pressure seems to fade away a bit quickly. But there is no Bosch spec for it. Your fuel pressure is too low. Must be 2.0 to 2.1 Bar on running engine. But that should not create such low CO.

Noted with thanks, I won't apply 12V pulse. Btw, just curious, what are the behavior of the injectors that would cause a low CO? What should I observe (e.g., volume, spraying angle)?

Too little volume and a stream instead a spray would cause low CO.

Hi there. I have some updates to share:
I have installed the ECU repaired and shipped a week before from BOSCH Classics. It is the second time I work on the ECU.
When I test drive happily with my MB 280SEL, it can perfectly start and drive it. After starting 30sec to 1 minute, there is sawing sound (it is not a problem), then after another 1 minute, it could run perfectly.

The problem is, after a few days of joy ride, the car was cranking but not running yesterday. I quickly check the D-Jetronic system of the car, and the result is below:
1) I unplugged 8 injector wiring plug and install 8 LED light to the wiring plug for testing
2)when IGN ON, cylinder 4,8 has light on, while cylinder 3 & 6 has flashed once.
3) when cranking, only cylinder 2&7, 4&8 have flashing light

I started to think it is the ECU fault, but I have high trust to BOSCH's work. May I ask for guidance if there is any other possible fault that I missed here? Thanks a lot!

IGN ON video:
drive.google.com/file/d/1AJfH3j4KEibGgKW...Ep0/view?usp=sharing

Cranking video:
drive.google.com/file/d/1AJYQzLGOoDKMlX8...8Im/view?usp=sharing

Best regards,
Danny

Hi Danny,

if 1&5 and 4&8 are missing pulses, it means that pulse generation on both tracks in ECU work. Following issues are possible:

1. Trigger contact fault - we have measring gauge and replacement cams
2. Wiring harness TC to ECU fault
3. ECU fault
4. Wiring harness ECU to injector fault
5. Grounding fault of injectors

I propose that you measure signals from TC to ECU

Thanks for your prompt reply and guidance as usual! I followed your instruction and replaced 4 trigger cam with correct clearance 0.45~0.50mm, then inspect:
1) unplug the trigger connector and measure pin 12,13,14,21,22 at distributor, which are all normal without short body
2) unplug ecu connector and use multimeter to measure trigger close and open. When cranking, pin 12~13, 12~14, 12~21, 12~14 have close and open (all normal)
3) unplug ecu connector, check connector power and earth. When IGN ON, pin 24~11 has 12v and pin 16~11 has 12v
4) plug back the ecu connector, measure trigger signal at the back of the ecu connector. When cranking, pin 12~13, pin 12~14, pin 12~21, pin 12~22 have flashing LED light, which means trigger has been sending correct signal to ecu
5) measure signal from ecu to injector at the back of the ecu connector. pin 3 (1, 5cyl.)~eath with no flash, pin 4 (4, 8 cyl.)~earth with flash, pin 5 (6, 3 cyl.)~earth with no flash, and pin 6 (7, 2 cyl.)~earth with flash, which means pin3 & 5 have no signal output

Pin12~13 (multimeter)
drive.google.com/file/d/1B0DwMTiGMij_QJf...tSQ/view?usp=sharing
Pin 12~13 (flash light)
drive.google.com/file/d/1AlsJz-1Bw-hRjzq...EF8/view?usp=sharing
Pin3 and pin 5
drive.google.com/file/d/1B2oTbPRAPWbHOx9...rRI/view?usp=sharing
Pin4 and pin 6
drive.google.com/file/d/1B5ZFkbneiyAozmg...ZuF/view?usp=sharing

Appreciate your help again!

Best regards,
Danny

Hi Danny,

if you have correctly measured then your ECU has a fault. Trigger contacts come in but 2 of4 injector groups do not work.

Hi Danny,
I remember your ECU and MAP were tested in Hildesheim at Bosch factory about 10 months ago as being error-free.
I think your ECU has been infected by the Goldie-virus.
(Don't think about this, it's meant for Volker)
But I think - like Volker does - your ECU has a fault that comes and goes... yes, it's not the only ECU with this behavior.

Fatal situation.
I can't help you - don't have Mercedes-stuff in stock.

Regards
Norbert

Hi Danny,

if you were in Germany or EU I would offer to check your ECU. However I am careful with a remote diagnosis. If Bosch has verified your ECU I would not maintain that it is broken without having seen a swap with another ECU that does not show the fault.

Many thanks to Mr.Nordfisch and Dr.Djet Volker for your prompt replies and guidance.
Mr.Volker provides that the following 5 items may fault:
1) Trigger contact fault
2) Wiring harness TC to ECU fault
3) ECU fault
4) Wiring harness ECU to injectors fault
5) Grounding fault of injectors
I am sure that items 2, 4 and 5 are 100% ok
For item 1) “Trigger contact fault”, I did not have a professional equipment to check, so I could only replace 4 trigger contact cams as suggested by Mr. Volker. I used the "Norbert's special plug gauge" tool I purchased many years ago and followed its instructions to adjust the clearance 0.45mm to 0.50mm then use Noid light and multitester to check that all 4 triggers have open and close actions.
As for the item 3) "ECU fault", I don't have the knowledge or equipment to check whether it still has a fault. I can only send it to Bosch for check-up, but I was told twice by BOSCH that the ECU is not faulty, which makes me very confused.
The first time it was inspected by Bosch and sent back to me for installation, the co was only 0.02~0.08 and could not be adjusted to the correct 1.5~2.5
After the second inspection from Bosch, it was sent back to me and installed on the car. The co was adjustable to normal 1.5~2.5, but the car only ran for a few days before the above situation occurred:
IGN ON, There is Noid light signal in 4 and 8 cylinder injector wiring connector (Is this normal?)
CRANKING, Only 4, 8 and 7, 2 cylinder injector wiring connector have Noid light signals.
Apart from ECU failure, I can't think of any other fault that would have this behavior.
Fortunately, I found a brand new ECU in Hong Kong that had been stored for many years for me to test.
Besides Bosch, any other third party could check whether my ECU is faulty?
I hope experts here can provide suggestions, comments and help to me! Thanks again!

Best regards,
Danny